Field of the Invention
The invention relates in general to a power amplifier circuit and an operating method thereof.
Description of the Related Art
The power amplifier circuit has been widely used in various electronic devices for converting an input signal into an output signal with larger power for transmission purpose. Generally speaking, the power amplifier has better output efficiency when the power amplifier is operated in a saturation region. However, in order to satisfy the amplitude variation for transmitting the modulation signal or due to power saving consideration, the power amplifier is usually operated in a back-off region having a lower output power to satisfy the linearity requirement or other system requirements. However, the power amplifier efficiency will be decreased when operated in the back-off region.
Therefore, it has become a prominent task for the industries to improve the efficiency when the power amplifier circuit is operated in a back-off region.